1. Field of the Invention
The present invention relates to an apparatus and a method adopted to identify the contour of a road by detecting a white line present on the road.
2. Description of the Related Art
There are apparatuses in the known art that obtain an image of a road with a camera mounted on a vehicle and detects a white line by processing the obtained image. The accuracy of the white line detection may become poor or the white line detection itself may become disabled in such an apparatus if the white line contrast is lowered as the white line becomes faded or due to a reflection of sunlight off the road surface. Accordingly, it is necessary to implement image processing in order to enable detection of the white line when its contrast is low.
Japanese Laid-Open Patent Publication No. 2000-335340 discloses a method for raising the contrast of an image captured by an on-vehicle camera. In this method, a density variation histogram is prepared from the captured image and density conversion is implemented so as to modify the densities within the range between the highest and the lowest density levels obtained in a uniform manner by excluding certain density levels at the two extreme ends in the histogram at a predetermined density level. In addition, the publication also proposes a method of image density conversion which is achieved by emphasizing a dark area or a light area based upon the relationship between the density level at the barycenter of the histogram and the central value of the density levels. The accuracy of object detection is improved by achieving better contrast in the captured image through either of these methods.